The invention relates to a bi-functional optical detector for detecting two wavelengths while eliminating background noise.
The purpose of this invention is to describe the architecture for combining two specific previously demonstrated functions of quantum well detectors, namely the possibility of making bi-spectral devices (French patent No. 2 756 667) and the possibility of making detectors integrating the subtraction function of the continuous component in the active layer, in other words the darkness current due to thermal causes and the optical scene current (French patent No. 2 756 666). Each of these two functions requires a double stack of quantum wells and a 3-stage connection. With the invention, this number of stacks and connection stages can be kept while enabling reading in subtractive mode according to three spectral curves, namely xcex1, xcex2 and xcex1+xcex2.
Therefore, the invention relates to a bi-functional optical detector comprising:
a first active photoconduction detection element capable of detecting a first range and a second range of wavelengths, associated with a first diffraction grating that it uses to couple the light from the first range of wavelengths in this first detection element, so that the first active photoconduction detection element can detect light in the first range of wavelengths;
a second active photoconduction detection element capable of detecting a first range and a second range of wavelengths, associated with a second diffraction grating that it uses to couple the light from the second range of wavelengths in this second detection element, so that the second active photoconduction detection element can detect light in the second range of wavelengths.
The invention also relates to a process for making this type of detector.